Intravascular medical device

ABSTRACT

An implantable medical device is configured so that all of the major components including a housing and attached leads are disposed within the vasculature of a patient. A tether extends from the housing of the device to an implant location where the tether is secured to tissue outside of the vasculature. In this manner, an intravascular medical device may be implanted at a location remote from final placement, delivered via the vasculature and anchored at the initial entry point.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/342,735, now U.S. Pat. Ser. No. 7,627,376 filed Jan. 30, 2006entitled “Intravascular Medical Device”, herein incorporated byreference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to medical devices and in particular,implantable medical devices.

2. Description of the Related Art

Medical devices related to managing, treating and providing therapy forcardiac conditions have changed and improved dramatically since theirinception. Cardiac pacing, as an example, originally required anexternal pulse generator that itself required external power. Whileproviding life sustaining therapy, patients were tethered to the powersource and of course, power failures could prove catastrophic. Portable,battery powered external pulse generators were developed and providedthe patient with the ability to be ambulatory; however, the pulsegenerator had to be carried by the patient. Furthermore, pacing leadswere exposed through the patient's tissue and extreme care had to beexercised to minimize the risk of infection or inadvertent withdrawal.

Subsequently, fully implantable, battery powered pulse generators wereprovided in a hermetically sealed housing. This housing was rather largeand was typically implanted in the abdomen of the patient, with leadsextending to the heart. The size of such a device often made it ratheruncomfortable and the implantation procedure was relatively invasive.

As technology improved, implantable medical devices (IMDs) have becomecontinuously smaller, while offering increased longevity, reliabilityand many more features and therapies. Epicardial leads that wereattached to an external wall of the heart were replaced with endocardialleads that are implanted transvenously, thus becoming minimallyinvasive. With these smaller devices, the housing was no longer placedin the abdomen but instead was implanted subcutaneously orsub-muscularly, often in the pectoral region. A “pocket” is formedunderneath the skin or muscle sufficiently large to receive the housingof the IMD. The exposed or proximal ends of the leads are then connectedto the housing and the incision is closed. While now routine, this isstill a surgical procedure that requires skill and the appropriatemedical facilities.

In general, patients are comfortable with these implanted devices andhave a full range of motion, without interference or hindrance. Somepatients feel the housing in the “pocket,” which may be physicallyand/or psychologically uncomfortable. Physically, some patients maypress against the housing during certain physical activities making thehousing noticeable. Even if not a hindrance or painful, simply “feeling”the presence of the device may remind that patient that they have amedical implant and/or medical condition and this alone may be troublingto that patient. Some patients develop a habit of pressing against thepocket and hence against the IMD and often rotating or twisting the IMD.Typically, IMDs that have one or more leads will have any excess leadlength coiled under (or around) the housing of the IMD. Thus, frequentpatient manipulation may cause portions of the lead(s) to twist or rub,potentially damaging the lead body or pulling the lead out of contactwith the targeted tissue. This is sometimes referred to as “twiddlerssyndrome.”

As the size and capability of IMDs has greatly improved, use of thesedevices has naturally expanded. This results in greater knowledge andacceptance among the patient population as well as within the medicalcommunity. As a result, caregivers are using IMDs with more frequencyand for new and diverse purposes. For example, pacemakers are used inpatients with various bradyarrhythmias. In such a patient, the heart'sintrinsic pacing function fails or is deficient and the IMD provideselectrical stimulation to maintain the proper heart rhythm. Such therapyis well known and is referred to above with the early, external pulsegenerators. Recently, the medical community has been using pacingtechnology in patient's whose heart rhythm is actually normal. Heartfailure patients often have normal rhythm and conduction; however, thisdisease causes the heart to enlarge. As a result the left and rightventricles are unsynchronized when they contract even though thedepolarization waveform triggering such a contraction was “timed”properly. Using cardiac resynchronization therapy (CRT), the left andright ventricles are paced, leading to a mechanical “resynchronization”of the left and right ventricular contractions. This not only leads tobetter immediate hemodynamic performance, but the heart itself oftenremodels itself (reducing in size) leading to an improvement in thedisease state.

Not only are new therapies and treatments developing, implantabledevices are now being used to collect sensor data for a variety ofpurposes. For example, implantable loop recorders (ILRs) are implantedsubcutaneously and record cardiac data, unobtrusively, for extendedperiods of time. This allows robust medical data to be collected that,as a practical matter, may be otherwise unattainable.

These are merely two examples that illustrate the ever increasing trendto beneficially use implantable medical devices with greater frequencyand for a wide variety of purposes that extend well beyond cardiac care.This presents a challenge to some caregivers who might want to use agiven device for their patient but do not have the necessary surgicalqualifications to actually implant the device. While such a patient mayalways be referred to another doctor, this adds cost and burden, somepatients may not follow through, and some caregivers may simply opt forother treatments in order to maintain their relationship with thepatient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of selected internal components of anintravascular medical device (IVMD) consistent with the teachings of thepresent invention.

FIG. 2 is a schematic illustration of the IVMD including a tether and alead.

FIG. 3 illustrates an electrode incorporated into the tether.

FIG. 4 illustrates an IVMD having multiple leads.

FIG. 5 is a sectional view of a housing of the IVMD.

FIGS. 6A-6B illustrate an IVMD having a lead and the tether coupled to acommon end of the housing.

FIGS. 7A-7B illustrate a system for deploying the lead and housing.

FIGS. 8A-8D illustrate an IVMD having a tether with a lumen.

FIGS. 9A-9D illustrate an IVMD having a tether with a lumen coaxial witha lumen through the housing and an attached lead.

FIGS. 9E-9H illustrate multiple lumens.

FIG. 10 illustrates a housing having multiple housing portions.

FIGS. 11A-11B illustrate multiple housing components with a commontether.

FIGS. 12A-12D illustrate a mechanism to attach a stylet to a housingcomponent.

FIGS. 13A-13B illustrate an IVMD with multiple housing portions.

FIG. 14 illustrates an IVMD having multiple housing potions and multipletethers.

FIG. 15 illustrates an interaction of a stylet with both tethers of FIG.14.

FIG. 16 illustrates an IVMD with multiple housing portions.

FIG. 17 illustrates an implanted IVMD.

FIG. 18 illustrates the anatomical relationship between the subclavianvein and the clavicle.

FIG. 19 illustrates the anatomical location of the cephalic vein.

FIG. 20 illustrates an IVMD implanted in the superior vena cava havingan auxiliary support member further anchoring the lead.

FIG. 21A-21J illustrate the insertion and anchoring of an IVMD.

FIGS. 22A-22B illustrate a tether anchor.

FIG. 23 is a flowchart describing a process for implanting an IVMD.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary intravascular medical device (IVMD) 10.The IVMD 10 is an implantable medical device that includes ahermetically sealed housing 12 containing components 18 to control,power, and operate the device. The housing 12 is shaped and configuredto reside entirely within the vasculature anatomy or within a givenorgan (e.g., the heart, lungs, kidney, pancreas, etc.) via thevasculature. In one embodiment, the housing 12 has an approximatediameter of 6-7 French. The IVMD 10 may have any number of functionalareas including sensing, diagnostic, communications and therapydelivery. In the illustrated example, the IVMD 10 includes cardiacsensing, pacing and defibrillation as well as the ability to communicatewith an external device through telemetry.

The housing 12 includes a proximal header 16 and a distal header 14. Theoperative components 18 include a power source 20, such as a battery.One or more capacitors 22 are provided that allow charge to beaccumulated for rapid discharge to deliver a defibrillation orcardioversion pulse. A pulse generator 26 is coupled to the power source20 and provides electrical stimuli for cardiac pacing.

A microprocessor 24, memory 36 (flash, EEPROM, ROM, RAM, DRAM, harddisk,etc.), analog to digital converter (ND) 30, analog signal processor 28,and digital signal processor (DSP) 32 are positioned within the housing12. An externally actuated switch 42 is provided and may take the formof a reed switch that is closed by a magnet. Such a switch 42 may beused to initiate a telemetry session with IVMD 10. Alternatively,communication may be initiated directly by an RF signal or otherappropriate transmission medium. A telemetry module 34 provides theability to transmit and receive data. A reservoir 35 is optionallyincluded. The reservoir may provide a supply of a deliverable drug(e.g., insulin), genetic material, or biologic. The IVMD 10 may providefor the release of the material on a given schedule or based upon sensedneed. Some materials, such as insulin, may be dispersed as needed butare predictably used; that is, the likelihood of delivery over a giventime period is high. Other material may be delivered on an acute basis.For example, a dose of a blood thinner, coagulant, anti-coagulant, oradrenaline is provided and released when necessitated.

An accelerometer 40 may be utilized to provide an indication of patientactivity for a rate response function and/or a relative positionindicator; that is, physical position of the patient (e.g., prone).Finally, a sensor array 50 is illustrated. The sensor array 50 may senseany number of parameters such as temperature, pressure, velocity orother fluid flow characteristics, impedance, motion or size (e.g.,ultrasound for wall motion and/or chamber size), oxygenation, glucose,or the level of any sensed chemical substance. It should be appreciatedthat while illustrated as contained within the housing 12, the sensorarray 50 may have appropriate external portions not shown. For example,if used as a pressure sensor, a transducing membrane will form a part ofhousing 12 or part of a lead coupled with the housing 12, eitherphysically or through telemetric connection (e.g., a body bus).Likewise, any additional component(s) for sensor array 50 will beincluded in this manner, as required. Cardiac data (e.g., electrogram(EGM)) will be sensed via one or more leads as explained below. Inaddition, the housing 12 may include one or more electrodes incorporatedinto the structure of the housing 12 (i.e., an active “can”).

As indicated the power source 20 may be a single use battery.Alternatively, the battery may be rechargeable. As such, an optionalrecharging module 25 is illustrated. The recharging module 25 mayreceive power from an external source, such as directed RF energy, whichis converted and used to recharge the battery 20. The RF energy may becollected via one or more antenna as discussed below, by using thehousing 12 as an antenna, or by incorporating a receiver into thehousing 12. Alternatively, or in addition, the recharging module 25 mayuse other mechanisms to generate power. In one embodiment, heat fromwithin the patient is converted into current. In another embodiment,chemical energy from cells proximate the implant location is convertedinto electrical energy by the charging module 25. The charging module 25may convert body motion into electrical energy. Such motion may comefrom multiple sources including without limitation gross patientmovement (walking, exercising, etc.), lung motion (breathing), cardiaccontractions, vasculature contraction (pulsitile blood flow), or fluidflow. The length of the unit provides the ability to harness mechanicalpower at one or more flexation points. Such flexation points may occuralong the tether and/or in-between housing components. In this context,mechanical motion is converted into electrical energy by variousmechanisms such as movement of a magnetic member within a coil. Thecharging module 25 may also used photovoltaic conversion to generateelectrical current. A light collected placed sufficiently close to thesurface of the patient's tissue will receive enough ambient light toprovide power. Various other techniques are available to recharge thebattery and are considered to be within the spirit and scope of thepresent invention. The following documents are herein incorporated byreference in their entirety: U.S. Pat. No. 6,242,827, issued to Wolf etal. on Jun. 5, 2001; U.S. Pat. No. 6,768,246, issued to Pelrine et al.on Jul. 27, 2004; US Published Application 2004/0073267, published onApr. 15, 2004; and US Published Application 2004/0158294 published onAug. 12, 2004.

The module 25 has been described in conjunction with a traditionalrechargeable battery 20 as a mechanism to recharge that battery. Itshould be appreciated that to conserve space, the traditional battery 20may be eliminated or greatly reduced in size (due to a decrease inreliance upon the battery). That is, the various mechanisms described togenerate electrical energy from sources around the IVMD 10 may be usedto directly power the IVMD 10, without first storing that energy in abattery. This concept is applicable to any of the various forms the IVMD10. In one embodiment, providing power directly from module 25 isutilized when the IVMD has low or minimal power consumption requirements(e.g., periodic sensing). Thus, power is generated for internaloperations and when communication is desired, external power is providedfor e.g., telemetry functions, through inductive coupling or RF powertransmission. Of course, the IVMD 10 may be completely dependant uponsuch power conversion for all of its functionality. Finally, asindicated, a smaller battery or capacitor may be provided to collectsome amount of energy prior to use; either to mitigate againstfluctuation in the source (e.g., movement stops for a period of time) orto provide an even power supply to mitigate against power fluctuations;that is, to provide a relatively stable DC source.

FIG. 2 illustrates a lead 60 coupled with the distal header 16. One ormore electrodes are incorporated into the lead 60. As illustrated, lead60 includes a helical affixation member 64 that allows penetration intotissue to secure the distal portion of the lead 60 at a specific site.The helical affixation member 64 may serve as an electrode and/or thedistal end of the lead 60, proximal to the helical member 64, acts as anelectrode. A coil electrode 62 is positioned proximal to the distal endof the lead 60 so that when implanted, the coil electrode creates adefibrillation vector through an appropriate cardiac path with anotherelectrode of the IVMD 10. The length of the lead 60 and the relativeposition of the electrodes are selected based upon the type oftherapies, sensing and diagnostics provided and the implant location ofthe housing 12. The lead 60 may have other functions instead of or inaddition to electrical stimulation or sensing. For example, a number ofnon-electrical parameters (e.g., pressure, temperature, velocity,chemical presence/concentration, etc.) may be sensed by providing anappropriate sensor. The lead 60 may have a delivery device to deliverdrugs, genetic material, or biologics from the reservoir 35. Such adelivery device may include a needle 65 a for delivery into tissue; adisbursing tip 65 b (e.g., a porous surface for release into a fluidsupply or against a larger surface area); or a variety of other deliverymechanisms.

The lead 60 is connected to the distal header 16. The connection may bea permanent, integral formation. That is, the lead 60 and housing 12 arefabricated to form an integral unit or the lead 60 is permanentlyaffixed to the housing 12. Alternatively, the lead 60 is separable fromthe housing 12, as explained below. As used throughout, the designationsproximal and distal header 14, 16 are used to indicate particularportions of the housing 12. It should be appreciated, that theseportions may include a header in the traditional sense of an implantablemedical device. That is, a separate portion from the remainder of thehousing that includes various connection mechanisms (e.g., for receivinga lead connector pin). Alternatively, the terminology may simply referto a given end or portion of the housing 12 to facilitate description.

A flexible tether 70 extends from and is securely coupled to theproximal header 14. At a proximal end 74, the tether 70 has an anchoringpoint. In the illustrated embodiment, a T-shaped anchor member 76 isattached to the tether 70 at the anchoring point. The anchor member 76includes one or more suture ports 78 extending through the member 76. Asindicated, IVMD 10 is implanted transvenously and the entire housing 12resides within the vasculature or within an organ accessed via thevasculature. The tether 70 extends from the implanted location of thehousing 12, through the vasculature and is anchored at or near thevasculature incision or puncture created for implantation. Thus, thetether 70 will fully or partially maintain the position of the IVMD 10.For example, if implanted in the superior vena cava, with a pacing lead60 extending from the housing 12 into a cardiac chamber, blood flow andgravity (generally) will provide force against the housing 12 in adirection towards the heart. With the anchor point fixed, the housing 12is prevented from traveling towards the heart and is thus secured. Whilesuturing has been discussed, other methods of attaching or anchoring thetether 70 and/or the anchor 76 may be utilized.

The anchoring point 74 allows for subsequent identification and accessto the IVMD 10. That is, if the IVMD is replaced or modified, theanchoring point 74 is located and the IVMD 10 can be accessed or removedvia the tether 70 along the same vasculature pathway. As such, theanchoring point 74 may optionally include a radiopaque marker, may beconstructed of a biocompatible metal, or having other identifyingmechanisms to aid in determining the location of the anchor point 74 ata later time via X-ray, MRI, or other imaging techniques. Alternatively,the anchor point 74 may be positioned sufficiently close to the surfaceof the patient's skin that its location may be felt by applying pressureto the area.

The tether 70 is intended to secure the position of the IVMD 10 duringthe life of the implant. Accordingly, the tether material is constructedof a suitably strong, flexible, biocompatible material. The length ofthe tether 70 may include a drug eluting surface along the entireexterior, a portion of the exterior, or multiple distinct drug elutingsurfaces may be provided. In some embodiments, the tether 70 may be usedto temporarily secure the IVMD 10 until another anchoring mechanism isenacted (e.g., fibrotic growth). In yet another alternative embodiment,the IVMD 10 is intended to degrade within the body or pass harmlesslyout of the body. For example, IVMD 10 may be a chemical sensor and thetether 70 secures the IVMD 10 at an appropriate location within thevasculature, counteracting the forces of pulsitile blood flow.Eventually, the sensor will dissolve and in such an embodiment, thetether 70 could likewise dissolve. Of course, the tether 70 provides aconvenient mechanism to remove any such device thus providing fortemporary implantation of a variety of medical devices, includingpacemakers and defibrillators.

The tether 70 is provided with an excess length. After implantation ofthe lead 60 and housing 12, the desired length of tether 70 isdetermined. This final length should include enough excess to allow fornormal movement of the housing 12 within the vasculature as well as anyvariations that will occur due to patient movement, positioning, growthor other physiological variations. The tether 70 is then cut at theappropriate location and anchored into place. The T-shaped anchor member76, if used, is attached to the cut tether 70, either by suturing,mechanically clamping or using any other secure coupling mechanism.

As indicated, excess tether length is provided at the proximal end ofthe tether 70 with an expectation that this excess will trimmed orremain unused. This allows for flexibility during implantation andminimizes the need to have multiple pre-configured devices toaccommodate different patient sizes and implant locations. Conversely, adistal portion of the tether 70 will reliably remain intact. Thus, thisportion of the tether 70 may be used to provide additional structure orfunctionality.

As illustrated in FIG. 2, an antenna 72 extends from the housing 12 andmay be contained within or affixed to an outer portion of the tether 70.Including the antenna 72 within the tether 70 provides a hermiticenclosure for the antenna 72 and any exposed feedthrough. The length,size, shape and configuration of the antenna 72 may vary from theillustrated embodiment and may extend for a relatively long length ascompared to traditional implantable medical devices. The antenna 72 maybe used for communication and/or as an RF collector to receive power torecharge the power source 20. Furthermore, while one antenna structure72 is illustrated, multiple antennas may be provided to facilitatedifferent types of communication; to have a different antenna fortransmission versus reception; to provide a separate power collector, toprovide low and high power communication formats, to provide redundancyor for any number of reasons. One or more antennas may also be includedin the lead body 60.

FIG. 3 illustrates an alternative embodiment, wherein a distal portion80 of the tether 70 functions as a lead having an electrode 82 forsensing or stimulation. That is, the electrode 82 is electricallycoupled to the housing 12 via the distal portion 80 of the tether 70.This electrical coupling may be completely internal to and distinct fromthe tether 70 so that the mechanical properties of the tether 70 may berelied upon without adding stress or strain to what would be considereda lead body. The electrodes 62 and 82 may be positioned to facilitatedefibrillation across the vector defined. In another embodiment, theelectrode 82 acts as a pacing electrode. In yet another embodiment,element 82 is a sensor such as a pressure sensor. The antenna 72 of FIG.2 is not illustrated, though such an antenna may also be provided whenthe tether 70 includes one or more electrodes and/or sensors. Thestructure of the tether 70 may vary over its length. The distal portion80 is not intended to be severed. The proximal portion, in oneembodiment, is intended to be severed; thus, a transition point 84 maybe present. The tether 70 may have different materials and differentconstruction from one portion to another or may have a unitaryconstruction throughout.

FIG. 4 illustrates an embodiment having lead 60 and lead 100 extendingfrom the distal header 15. The second lead 100 is illustrated as havinga tined tip 110 for securement as well as a tip electrode 112 and ringelectrode 114. FIG. 4 is meant to illustrate that multiple leads maydepend from the distal header 15 and a variety of electrode andattachment (e.g., tines, helical tip) configurations may be employed.The use of two such leads is not meant to be limiting and any number ofadditional leads may be provided. Though not illustrated, one or moreadditional electrodes may be present on tether 70, as illustrated inFIG. 3.

FIG. 5 illustrates a sectional view of housing 12. In particular,multiple connection ports 150, 152, 154 and 156 are illustrated in theproximal and distal headers 14, 16. Port 150 includes a cavity 160shaped to receive a male connecting pin from, e.g., a lead. A set screw162 is positioned to advance into the cavity 160 and engage theconnecting pin, thus securing the pin in place. Access to the set screw162 is gained through a set screw opening 165 that may include a selfsealing material, such as silicone to reduce fluid entry into the setscrew opening after implantation. The configuration of port 150 isrepeated in each of the illustrated ports 152, 154 and 156. More orfewer ports may be provided as necessary and alternative configurationsmay be employed. When used to received and secure a lead 60, the leadpin will make contact with one or more electrical connectors disposedwithin cavity 160. The tether 70 may also include a connector pin thusallowing for connection to the housing 12 in the same manner as a lead.Of course, if the tether 70 includes electrode(s), antennas or othercomponents appropriate electrical contact is made via the pin andcavity. In the absence of such components, the tether is simplymechanically secured within the port 154, 156. As indicated, the tether70 may be integrally formed with the proximal header 14, thusappropriate access to ports 154, 156 (if provided) is facilitated by theconfiguration of the tether 70 or by providing access through a portionof the tether 70.

FIGS. 6A and 6B illustrate an alternative multiple lead configuration.In this embodiment, lead 60 is coupled with the distal header 16. Asecond lead 100′ is coupled with the proximal header 14 as is the tether70. In some applications, it may be desirable to have the second lead100′ extend in the same direction as the tether 70, and as such,connection to the proximal header 14 is straight forward. Alternatively,and as illustrated, the lead 100′ is extended in the same direction asthe first lead 60 (i.e., distal to the housing 12). When coupled withthe proximal header 14, the lead 100′ is bent to achieve thisconfiguration. While this is non-problematic for the lead 100′, movementof the housing 12 via the tether 70 (e.g., retracting the housing 12)may be more difficult. To permit and facilitate such movement, the lead100′ is bent to provide sufficient excess so that the housing 12 maymove relative to the lead 100′ without affecting the tip placement. Itshould be appreciated the lead 60, extending from the distal header 16also includes a certain amount of excess to address normal movement ofhousing 12 caused by pulsitile blood flow as well as some movementcaused by withdrawal or retraction of the tether 70.

The curvature in the lead 100′ may simply be imparted during implant,with the housing 12 remaining separate from the lead 100′ other than atthe proximal header 14. Alternatively, as illustrated in FIG. 6B, aguide member 180 may be provided on an outer portion of the housing 12.The lead 100′ passes through the guide member 180 maintaining the lead100′ in close proximity to the housing despite the imparted curvatureand any resulting bias. In addition, by appropriately sizing the guidemember 180 and providing a material with a low coefficient of friction(e.g., parylene, silicone) on the guide member 180 and/or the lead 100′,the housing 12 may be slid relative to the lead 100′.

For clarity, lead 60 is not shown in FIG. 6B. It should be appreciatedthat more than one lead may be coupled to the proximal header 14 in themanner illustrated. Furthermore, even if a single lead is employed, thatlead may be coupled as illustrated by the lead 100′ in FIGS. 6A and 6B.This would allow all connections to be made at one end of the housing 12while still permitting lead advancement in a direction opposite to thatof the tether 70.

FIGS. 7A and 7B illustrate a system including a device that will aid inpositioning any of the illustrated leads as well as the housing 12. Asteerable stylet (or catheter) 200 has a handle portion 202 at aproximal end that includes controls that cause the stylet to flex orbend to facilitate intravascular navigation. A releasable clampingmember 210 is positioned at or near a distal end of the stylet 200. Theclamping member is illustrated schematically in FIG. 7B as a sectionaltaken about the line A-A of FIG. 7A. Upon actuation of the handleportion 202, the clamping member 210 opens and closes pivoting arms 212so that lead 100′ (or tether 70) is gripped or released. In this manner,the lead 100′ is directed to a target location and the clamping member210 is opened, releasing the lead 100′. It should be appreciated thatthe stylet 200 could be navigated as an over the wire catheter, thusfollowing a previously positioned guidewire. The clamping of the lead100′ would remain the same; however, the stylet/catheter 200 would beguided by the guide wire as opposed to being navigated independently. Asindicated, such a device may be used to position leads coupled witheither the proximal head 14 or the distal header 16 and may be used toposition the housing 12. To position the housing 12, the clamping membermay be secured to a portion of an attached lead or to the tether 70.Implantation in this manner will be facilitated if the clamping occursrelatively close to the housing 12. Alternatively, a lead extending fromthe distal header 16 may be gripped at any position distal to thehousing 12, so that advancement of the lead with stylet 200 advances thehousing 12 as well.

FIGS. 8A-8D illustrate another embodiment wherein a steerable stylet 250is used to position the housing 12. FIG. 8C is a sectional view takenabout the line A-A in FIG. 8A and FIG. 8D is a sectional view takenabout the line B-B in FIG. 8A. In this embodiment, the tether 70 has alumen 254 sized to receive the stylet 250. While the T-anchor 76 isillustrated as being coupled with the tether 70, it should beappreciated that the T-anchor 76 may be attached afterwards and hence isnot utilized with the stylet 250 or the T-anchor 76 includes athroughbore that aligns with the lumen 254, thereby permitting passageof the stylet 250. In this embodiment, an abutment 252 is provided on anexterior of the housing 12, as part of proximate header 14. Thus, as thestylet 250 extends through the lumen 254, the tip of the stylet 250 willeventually reach and strike the abutment 252. Continued advancement ofthe stylet 250 will cause advancement of the housing 12 within avasculature pathway. If advanced too far, the tether 70 may beretracted, thus retracting the housing 12. As such, the housing 12 maybe implanted at a target location by using the stylet 250 for forwardadvancement of the housing 12 and the tether 70 for any necessaryretraction. Leads (not shown in these figures) may be implanted with thestylet 200 previously described or similar mechanisms, if utilized. FIG.8C also illustrates how the antenna 72 (if included) is positionedoutside of the path defined by lumen 254, which is congruent withabutment 252.

FIGS. 9A-9D are similar to FIGS. 8A-8D. In this embodiment, the lumen254 extends through the housing 12 as well as the lead 60. Thus, thestylet 250 may be advanced all the way through the tether 70, thehousing 12 and the lead 60 until it abuts an end of the lead 60. Thus,navigation of the stylet 250 will direct the distal end of e.g., lead 60which pulls the housing 12, ultimately positioning that component aswell.

FIGS. 9E-9H illustrate an embodiment having multiple lumens 254 a, 254 bthrough tether 70, housing 12 and lead(s) 60, with the second lead notillustrated. In this manner the stylet 250 can be directed through aspecific lumen 254 a, 254, to engage a particular lead separately fromanother lead. As should be apparent, more than two lumens 254 a, 254 bmay be provided to permit more than two leads or other appendages to bedirectly manipulated by the stylet 250. Further, the size, spacing andconfiguration of the lumens 254 may be varied. In an alternativearrangement, more lumens are provided through the housing 12 and coupledwith a corresponding lead than are provided through the tether 70. Thatis, the stylet 250 is directed through a lumen in the tether 70 and intoa larger opening within the proximal header 14. The tip of the stylet250 is then manipulated to manually select from a plurality of lumenseach extending from this opening through the housing 12 to a particularlead.

While direct manipulation of the stylet 250 to select a desired lumenwithin the housing 12 is one option, alternative arrangements areavailable. For example, the tip of the stylet 250 may be sized or shapedto specifically engage only one lumen through the opening in theproximal header 14. For each such lumen engaged, the tip may beexchanged or a different stylet 250 may be utilized. As an example, thelargest tip may be inserted through the common lumen in the tether 70and will only access the largest sub-lumen passing through the housing12. While occluding this larger opening, the next smaller tip may beutilized, and again a specific sub-lumen provides the only passage.

As described, the IVMD 10 may include multiple leads with each of theseleads attached or coupled with the housing 12. Due to the size andimplant location of IVMD 10, particular configuration of the housing 12may make attachment of more than two leads cumbersome. In fact, inembodiments, the use of more than one lead may be cumbersome. In such acase, the present invention provides for the use of multiple IVMDs 10,each having one or two leads. The separate IVMDs 10 are in wirelesscommunication so that their activities are synchronized. For example,one IVMD may provide atrial pacing and another may provide ventricularpacing. The multiple IVMDs 10 may be completely independent and simplycommunicate to one another to synchronize timing. Alternatively, oneIVMD 10 may act to control the functions of one or more other IVMDs. Themultiple IVMDs 10 may be implanted through the same entry point andreside in the same anatomical location or proximate one another (e.g.,both within the superior vena cava but offset from one another).Alternatively, the multiple IVMDs may be implanted from differentlocations and reside remotely from one another, while retaining wirelesscommunication.

FIG. 10 illustrates an embodiment wherein housing 12 is separated intotwo components 12 a, 12 b. The housing components 12 a, 12 b areoperatively coupled together with a flexible interconnect 300, which mayinclude one or more wires, cables or fibers for electrical or datacommunication. Alternatively, the flexible interconnect 300 may be asolely a mechanical coupling with each housing component 12 a, 12 boperating independently. For example, each may have separate functions.Alternatively, the housing components 12 a, 12 b are mechanicallycoupled and communicate in a wireless medium such as RF. Due to theirclose proximity, they may also be inductively coupled both for datacommunication and power transmission functions. Thus, the flexibleinterconnect 300 will mechanically connect the separate housingcomponents 12 a, 12 b and may provide electrical, data and/or powercouplings. As such, the flexible interconnect 300 will act like tether70′ as between housing component 12 a and housing component 12 b. Thatis, securing the proximal end of tether 70′ will ultimately retrainhousing component 12 b through the flexible interconnect 300.

FIG. 10 also schematically illustrates a simplified tether 70′ ascompared to the tether 70 illustrated in previous embodiments.Simplified tether 70′ is a generally linear, flexible member such aswire or cord and may be monofilament or multi-filar. The simplifiedtether 70′ could be secured to an anchor member such as the T-anchor 76,which is then secured to tissue. Alternatively, the simplified tether70′ could be sutured directly to tissue.

FIGS. 11A and 11B illustrate another embodiment including multiplehousing components 12 a and 12 b. As shown, housing component 12 aincludes the lead 60 extending from a distal end 16. The tether 70extends in an opposite direction from the proximal end 14. A threadedreceptacle 310 is axially aligned with a lumen 254 (FIGS. 8-9) throughthe tether 70. The second housing component 12 b includes a through bore320 sized to receive the tether 70. Thus, the housing component 12 b maybe added to or removed from the component 12 a subsequent toimplantation of component 12 a.

The housing component 12 a includes one or more receiving channels 314a, 314 b that receive corresponding connector pins 312 a, 312 b. Theengagement of connector pins 312 within channels 314 allows for amechanical coupling as well as optionally providing for electricalconnection through one or all of the connections. The connector pins 312are provided with biased protrusions 316 a, 316 b received withindetents 318 a, 318 b; thus, locking the connectors pins 312 into thechannels 314 when full inserted. Initial insertion as well as subsequentrelease of the connector pins 312 may require retraction of theprotrusions 316 internally via a mechanism that is not illustrated;thus, providing a secure locking mechanism. Alternatively, the springbias of the protrusions 316 may be overcome by applying sufficient forcein an axial direction. Thus, a locking action is formed that willmaintain the connection of the two housing components 12 a and 12 bwhile implanted, but does not require additional components forengagement and/or disengagement. It should be appreciated that the size,shape, location, and configuration of the pins 312 and channels 314 maybe varied in numerous ways while remaining within the spirit and scopeof the present invention.

In FIG. 11B, housing component 12 a is coupled with housing component 12b. Also illustrated is a stylet 322 having a threaded, tapered tip 326.The stylet 322 is inserted through the lumen 254 with the tether 70. Thestylet 322 is advanced until the tip 326 reaches the threaded receptacle310. Rotation of the stylet 322 then causes the threaded tip 326 toengage the receptacle 310. Once so engaged, linear movement of thestylet 322 will correspondingly move the housing component 12 a (and 12b if coupled as illustrated). Furthermore, once fully engaged, rotationof the stylet 322 in a clockwise (with standard threading) directionwill rotate the housing component 12 a. Use of the stylet 322 in thismanner allows for greater positional control of the housing 12 a withinthe vasculature. While retraction of the tether 70 allows for grossmovements, the engaged stylet 322 permits more precise movement whichfacilitates the attachment or detachment of housing component 12 b,among other things.

In one embodiment, the stylet 322 is advanced through the tether 70 andthreaded into the component 310. The housing receptacle 12 b is thenadvanced over the tether 70 using another stylet (see e.g., FIG. 13B) topush the housing 12 b. When the housing components 12 a, 12 b areproximate one another, stylet 322 is used (alone or in combination withtether 70) to hold housing component 12 a in place and rotate housingcomponent 12 a to align with housing component 12 b. When so aligned,the housing components 12 a, 12 b are joined. It should be appreciatedthat engagement mechanisms may be provided between housing member 12 a,12 b that do not require specific alignment. That is, a retaining clip,channel or other member may extend about the circumference of the headerof one housing component and a corresponding component may extendcircumferentially (fully or partially) about the corresponding header ofthe other housing component; thus, relative rotational positioningbetween the two housing components is irrelevant to engagement so longas general axial alignment is provided. For example, rather than havingchannel 314 discretely receives a single pin 312, the channel 314 mayextend circumferentially around the proximal planar face of the housingcomponent 12 a. Thus, the pin(s) 312 may be received anywhere along thischannel 314. Relative rotation is permitted even when protrusions 316and detent 318 (which may also be circumferential) are utilized.Alternatively, the detent(s) 318 may remain discrete and rotation of thehousing components 12 a, 12 b will cause engagement.

FIGS. 12A-12 D illustrate another embodiment of stylet 322. FIGS.12A-12C are side sectional views of a tip portion of the stylet 322.Initial engagement of the threaded tip 326 may be made more difficultsince the housing component 12 a is relatively free to rotate whenimplanted. The stylet 322 in the present embodiment includes an outersheath 350 and an inner rod member 352. The threaded tapered tip 326retracts and extends from the outer sheath 350.

One or more pins 340 extend from the outer sheath 350, with two suchpins 340 a, 340 b illustrated. The pins 340 are sized to easily engageopenings 342 (with 342 a and 342 b illustrated). It should beappreciated that more openings 342 may be provided than pins 340 toagain ease initial engagement. As illustrated in FIGS. 12A and 12D, thetip 326 is initially retracted within the sheath 350 and the stylet 322is spaced from housing 12. The stylet 322 is advanced until the pins 340engage the openings 342, as shown in FIG. 12B. Rotation of the stylet322 may be necessary to achieve this engagement. Again, the fit of thepin 340 to the opening 342 need not be particularly tight. Subsequentrotation of the stylet 322 will cause the pins 340 to abut a surface ofthe openings 342. Subsequently, the rod 352 may be advanced via controlat a handle 360 and rotated so that tip 326 is threaded into thereceptacle 310, thus achieving a secure engagement so that subsequentmanipulation of the stylet 322 will directly control the housing 12.

FIGS. 13A and 13B illustrate another embodiment utilizing multiplehousing components 12 a, 12 b. In this embodiment, the tether 70 iscoupled with housing component 12 a and housing component 12 b is slidover the tether 70. A stylet/catheter 400 is provided that includes alumen 410 sized to receive the tether 70. Thus, the stylet 400 is alsoslid over tether 70 and is used to push housing component 12 b intoengagement with housing component 12 a. Though not separately shown, itshould be appreciated that the stylet 400 may be releasably secured tohousing component 12 b so that advancement, retraction and rotation ofthe housing component 12 b is facilitated. The manner in which stylet400 is releasably secured to housing component 12 b may vary and mayinclude without limitation any of the coupling arrangements discussedherein.

FIG. 14 illustrates an embodiment of a multi component housing 12,wherein the distal housing component 12 b includes a supplemental tether450. The supplemental tether 450 may be permanent or temporary. Ineither case, the tether 450 may be used to retract housing component 12b while a device such as stylet 400 is used to advance the housingcomponent 12 b. When permanent, the supplemental tether 450 may beseparately sutured at a distal end for securement or may simply beaffixed to the tether 70.

FIG. 15 is an embodiment similar to that of FIG. 14. In this embodiment,the stylet 400 includes an outwardly extending tab 460. As the stylet400 is rotated (in either direction), the tab 460 will engage thesecondary tether 450, causing the housing component 12 b, to rotate withthe stylet 400. Thus, the stylet 400 is used to advance and rotate thehousing component 12 b, without any other coupling required and thesecondary tether 450 is used to retract the housing component 12 b.

More than two housing components may be coupled together to form ormodify the IVMD 10. As previously indicated, different parts of the samedevice may be separated between housing components. Alternatively or inaddition, subsequent housing components may be added to provideadditional therapies, diagnostics, capabilities or power. For example,an IVMD 10 may be implanted with a single use (i.e., non-rechargeable)battery. At a later point, another housing component may be added thatincludes a power supply to replace the depleted or soon to be depletedsingle use battery. Thus, the useful lifetime of a given device may beextended with a relatively minor procedure. An IVMD 10 may initially beimplanted having pacing functions and a later module may be added thatprovides defibrillation therapies. FIG. 16 illustrates one embodiment ofIVMD 10 having four joined housing components 12 a, 12 b, 12 c and 12 d.It should be appreciated that any number may be joined using anycombination of the embodiments discussed herein. It should further beappreciated that each such component need not have the same size andshape. This will depend upon the components included in any givensection of housing 12 and may take advantage of variations in thevasculature anatomy.

The IVMD 10 may also be accessed post implant to add components (asdiscussed above) or to exchange components. That is, rather than simplyadding a housing component 12 having an additional battery 20, a housingportion 12 having the battery 20 is first removed over the tether 70 anda new housing portion 12 is added. In this manner, the lead(s) 60 mayremain in place, while other portions of the device are removed,replaced or otherwise manipulated. To that end, it should be appreciatedthat the distal header 16 may take the form of a full or partial housingcomponent 12 that remains in place and is tethered to allow otherhousing components to be manipulated. Alternatively, the tether 70 maybe coupled with a distal portion of the lead(s) or lead connector. Thus,the entire housing 12 may be added/removed while the lead(s) remainsimplanted and tethered. Finally, it should be appreciated that the IVMD10 may provide a variety of functions including sensing, diagnosticsand/or therapy. Thus, accessing the IVMD 10 via the tether 70 allows forother components to be exchanged without removing the entirety of thedevice. For example, chemical sensors may become depleted of a sourcematerial or catalyst and replaced in this manner. Similarly, longer termdrug eluting member or drug reservoirs may be replaced. Such reservoirsmay contain traditional pharmaceuticals and/or genetic materials orbiologics. The IMVD 10 may be used to deliver such agents (e.g., genetherapy) to a target tissue location. When necessary, the IVMD 10 isre-supplied without requiring complete extraction or the implantation ofanother device.

FIG. 17 illustrates an IVMD 10 implanted within the subclavian vein 504and extending into the superior vena cava 506 of a heart 500. The lead60 is illustrated as being an atrial pacing lead and a distal tip 64 isaffixed within the right atrium 502. Multiple additional leads may beincluded. The tether 70 extends from the proximal header 14 of thehousing 12 through the subclavian vein 504. The proximal end 74 of thetether 70 exits the subclavian vein 504 at an initial entry point 600.The proximal end 74 is secured to tissue surrounding the initial entrypoint 600, by e.g., the T-shaped anchor 76 which is sutured to thetissue. As pulsitile blood flow, directed towards the heart 500, andpatient movement will cause movement of the housing 12, a sufficientamount of slack material is provided along the length of the tether 70.

The position of housing 12 illustrated in FIG. 17 is non-limiting. Ifdesired, the housing 12 may be positioned closer to the initial entrypoint 600, thereby increasing the length of the lead 60. Conversely, thehousing 12 may be positioned closer to or even within the heart 500,increasing the length of the tether 70 and decreasing the necessarylength of the lead 60. FIG. 18 illustrates the position of the heart 500relative to the subclavian vein 504 as well as the clavicle 620. In someembodiments, it may be desirable to position the housing 12 within thesuperior vena cava 506 below (towards the heart 500) the clavicle 620.This avoids any potential for “subclavian crush” wherein leads orcomponents within the vasculature are compressed between the clavicleand the first rib (not illustrated). The size and nature of a given IVMD10 will determine whether this is or is not a concern. Due to its size,shape and material properties, this will generally not affect the tether70. Furthermore, implantation via the subclavian vein 504 is only oneentry site and others may be utilized.

As illustrated in FIG. 17, the initial entry point 600 may be positionedquite distant relative to the location of the housing 12. FIG. 19illustrates the position of the cephalic vein 660 which flows into thesubclavian vein 504 and is accessible along the arm 665 of the patient.Thus, the initial entry point 600 may be made in the cephalic vein 660with the tether 70 then anchored to tissue in the arm 605.

After implantation, it may be necessary or desirable to access the IVMD10. The proximal end 74 of the tether 70 is located and, e.g., thesubclavian vein 504 is accessed. The housing 12 may be moved orremoved/explanted via the tether 70 and any associated leads 60 canlikewise be moved, explanted, tested or otherwise manipulated. Inaddition, components may be added or replaced on housing 12 withoutrequiring removal. As identification of the proximal end 74 of thetether 70 facilitates such procedures, the proximal end 74 may include aradiopaque marker for identification with various imaging technologies,such as X-ray imaging or fluoroscopy. Of course, the entirety of thetether 70 may likewise be radiopaque. Alternatively, or in additionthereto, the proximal end 74 may be felt by applying pressure in thearea. The configuration and anchoring of the proximal end 74 willdetermine whether this is possible and a balance is selected betweenpatient perception of the proximal end, and the ability to locate thetether 70 manually, and the ease or pressure required to locate thetether 70 manually. As yet another alternative, the subclavian vein 504(or any vein/artery with a tether 70) is accessed via a new puncturedistal to the proximal end 74. The tether 70 is then located andmanipulated. This may involve severing the tether 70 and if appropriate,reattaching or re-anchoring the tether 70.

As illustrated in FIG. 17, the IVMD 10 is secured at two locations; thefirst being where the proximal end 74 of the tether 70 is sutured andthe second where the lead 60 is affixed to the atrial wall. In someembodiments, the nature of the lead 60 (or the absence thereof) maypermit the distal end of that lead 60 or the housing 12 to move freelyand remain unsecured. For example, lead 60 may include a pressure sensoror temperature sensor. While such sensors may still include anattachment mechanism, it is possible to permit them to remainunattached. In addition to having the tether 70 anchored and having oneor more leads 60 anchored, the flow of blood is directed towards theheart; which generally assists with maintaining the position of housing12 as this flow generates force against the anchored portion of thetether 70. This represents a relatively simple implantation procedure inthat additional retention mechanisms are not required.

As indicated, the subclavian vein 504 and superior vena cava 506 are notthe only potential implant locations. A variety of other locations willbe able to utilize blood flow and gravity in combination with the tether70 to secure IVMD 10. Of course, IVMD 10 may be implanted in otherlocations wherein this effect is not available or sufficient. Inaddition, there may be other reasons to further secure various portionsof IVMD 10. In one embodiment, retractable members are provided thatexpand against a vessel wall to secure the IVMD 10. The retractablemembers are collapsed for subsequent movement or explantation. Suchstructures are illustrated in published PCT application WO 2004/110263which is herein incorporated by reference.

FIG. 20 illustrates an IVMD 10 implanted in substantially the sameposition as illustrated in FIG. 17. In this embodiment, an expansionmember 700 is expanded within the superior vena cava 506. Expansionmember 700 presses the lead 60 against an interior wall of the vessel,further securing the lead 60 in place. Expansion member 700 may be aself expanding member made from shape-memory material or from materialhaving a spring force that is restrained by e.g., a catheter untildeployed. Alternatively, expansion member 700 is mechanically expandedby a balloon catheter or similar deployment mechanism. The use of such amember is generally not required when both ends of the IVMD are securedand blood flow is not pulling against an implanted lead. Such anexpansion member may be useful when the lead 60 is otherwise unsecuredor IVMD 10 is positioned in a location where blood flow or other forcesmight negatively affect the implant. It should be appreciated that theexpansion member 700 may be used for one or more leads, the housing 12,the tether 70 or any combination thereof.

FIGS. 21A-21J schematically illustrate implantation of the IVMD 10. InFIG. 21A, a needle 810 is used to percutaneously pierce and enter avessel 802, such as for example the subclavian vein or cephalic vein.The needle 810 passes through the skin 800; in some cases access to thevein 802 may require piercing muscle or other tissue. Care is taken withthe percutaneously puncture so that the needle does not pass entirelythrough the vessel 802 and into the underlying tissue 804.

With the needle 810 positioned within the vessel 802, a guidewire 815 ispassed through the needle 810 and into the vessel, as shown in FIG. 21B.While retaining the guidewire 815 in place, the needle 810 is withdrawnas illustrated in FIG. 21C. A deployment catheter 820 is inserted (FIG.21D) into the vessel 802 over the guidewire 815. A dilation catheter maybe used to expand the original puncture or the tissue may be cut if theopening is insufficient. Depending upon the configuration of the IVMD10, the guidewire 815 and/or the deployment catheter 820 may be directedto the final implant location for a lead and/or for the housing of theIVMD 10. Alternatively, if a stylet or other external mechanism isutilized, the deployment catheter 820 need only provide access to thevessel 802 and the length of penetration is selected as desired.

The IVMD 10 passes through the catheter 820 and enters the vessel 802.Again, multiple embodiments have been presented and the order of entryof certain components will vary accordingly. In this example, the lead60 is directed first towards the implant site by e.g., a stylet directedthrough the lead or a stylet gripping an external portion of the lead;neither of which are illustrated in this figure. Trailing the lead 60 isthe housing 12 followed by the tether 70. When the housing 12 and lead60 are positioned, the tether 70 will include an excess amount exitingthe incision site as illustrated in FIG. 21F. If additionalintravascular securement mechanisms are utilized, they are deployed andconfigured. The tether 70 is cut (FIG. 21G) at sever point 830 with asufficient amount of excess provided so that upon anchoring, enoughslack remains to allow expected movement of the IVMD 10 within thevasculature. The cut tether now has a new proximal end 840.

The new proximal end 840 is secured. As discussed, there are multiplemethods to attach the tether 70. As illustrated, the T-anchor 76 ismechanically attached to the new proximal end 840 (FIG. 21H). TheT-anchor 76 is then secured with sutures 850 to tissue proximate theincision site (FIG. 21I). The puncture or incision through the vessel802 will heal around the tether 70 and if necessary, this process may beaided by additional suturing or other techniques. The T-anchor 76 willremain below the surface 860 of the skin 800, with the actualdepth/distance from the surface 860 determined by the medicalpractitioner, the depth of the incision, and the site of implant. Itshould be appreciated that the anchor 76 may be affixed to skin tissue,muscle or even the vasculature wall. The final position of the anchor 76may therefore be subcutaneous or submuscular. As illustrated in FIG.21J, the anchor 76 may be secured some distance from the vessel 802.This may require an additional minor incision, but allows the anchorpoint to be selected disparate from the puncture through the vessel 802.

FIGS. 22A and 22B are side elevational sectional views that illustratean external vasculature anchor 900 (EV anchor). As previously discussed,the T-anchor 76 is sutured or otherwise attached to tissue external tothe vessel 802. The EV anchor 900 is configured for direct attachment toan external wall of the vessel 802. The EV anchor 900 has an arcuateattachment pad 902 with a tether connection rod 904 depending therefrom.A tether attachment opening 906 is provided at a distal end of the rod904 so that the tether 70 is coupleable to the rod 904. The rod 904penetrates the vessel 802 (though the drawings are not meant to be toscale) and serves as the anchor for the tether 70. The arcuateattachment pad 902 is large in comparison to the rod 904 so that theforce generated against the vessel 802 is dispersed over a largersurface area.

The EV anchor 900 includes an interior concave surface 910 that isplaced in contact with the vessel wall. This surface 910 is subdividedinto a first region 915 proximate the rod 904 and the remainder of thesurface 920. Various drug eluting or traditional coatings may be appliedto the interior surface 910. For example, in the first region 915, wherethe rod 904 enters the vessel 802, adhesives, steroids, coagulants orother materials are provided to facilitate the closure and healing ofthe puncture. The second region 920 may be utilized for more adhesion orsimply for mechanical support. The attachment pad 902 is meant togenerally conform to the shape of the exterior wall of the vessel 802.To that end, the pad 902 may be flexible or malleable. Furthermore,while illustrated as extending about less than half the circumference ofthe vessels 802, it should be appreciated that the pad 902 may extendabout a greater portion of the vessel 802 and may completely surroundthe vessel 802.

FIG. 23 is a flowchart with an overview of the steps for implanting theIVMD 10 consistent with the teachings of the present invention and asdescribed in greater detail above. The appropriate point of entry (e.g.,subclavian vein) is identified and a percutaneous puncture is made(1000). If necessary, this opening is enlarged and any necessarycatheter, guidewire or stylet is utilized to insert, deliver and attachthe housing, leads and any other intravascular components of the IVMD 10(1010). The tether 70 extends from the now delivered housing 12 to theentry site and excess tether is cut and discarded (1020). Finally, thetether is secure external to the vessel so as to anchor the IVMD 10(1030).

While various embodiments have been shown and described, the presentinvention is not meant to be limited by these embodiments. Furthermore,the embodiments may be combined in numerous ways without departing fromthe teachings of the present invention, even when not specificallyillustrated. Variations and modifications may be made without departingfrom the spirit and scope of the present invention.

1. A method comprising: implanting a lead at an anatomical location;implanting a housing having a power supply within a vascular structure,wherein the lead is operably coupled with the housing; securing thehousing within the vascular structure with a tether that is anchored, atits proximal end, outside of the vascular structure; replacing the powersupply subsequent to implanting the lead, implanting the housing andsecuring the housing, without removing the lead from the anatomicallocation.
 2. The method of claim 1, wherein replacing the power supplyfurther comprises: accessing the tether post-implant; removing thehousing with the power supply; implanting a second housing with a secondpower supply by directing the second housing with the tether; couplingthe second housing to the lead, wherein the lead remains attached to theanatomical location.
 3. The method of claim 1, wherein replacing thepower supply further comprises: accessing the tether post-implant;removing a portion of the housing including the power supply whileleaving a tethered section of the housing; implanting a second portionof the housing including a charged power supply by directing the secondportion of the housing with the tether; coupling the second portion ofthe housing with the charged power supply to the tethered section of thehousing.